Although springless air horns are known in the prior art, the types of air horns prevailing in the present market require that the horn diaphragm be subjected to spring loading in a direction forcing the diaphragm against the mouth of the duct for projecting resonated air into its trumpet. A common disadvantage of either the springless or the spring-loaded horns is that they must be adjustably tuned or parts, such as springs, made to very precise standards to obtain satisfactory operation. Moreover, these prior art horns, in general, are operable at undesirably narrow pressure ranges. This is a serious disadvantage if the tank pressures vary to any great degree, such as often happens in the case of unusual brake usage or leaks in the air system. Because of the mode by which a spring resists oscillation of the horn diaphragm, precision of spring loading to effect tuning is required on spring equipped horns with the result that such horns perform in a somewhat smaller pressure range than is satisfactory. In the prior art springless horns, the diaphragm itself provides the spring force and must be constructed to a thickness which provides the diaphragm resiliency required for an intended air pressure.
Hence, objects of the invention are (1) to devise an air horn with a minimum of parts which can be assembled to operative condition without the need for tuning adjustments, and (2) that a horn so devised will produce satisfactory horn sounds by application of air under a very wide range of supply pressures.